The present invention relates to viewing ribs in computed tomography (CT) volume data, and more particularly to a system and method for enhanced viewing of rib metastasis using CT volume data.
Computed tomography (CT) is a medical imaging method whereby digital geometry processing is used to generate a three-dimensional image of the internal features of a patient from a large series of two-dimensional X-ray images taken around a single axis of rotation. Such CT imaging results in CT volume data which is a virtual representation of internal anatomical features of a patient. The CT volume data consists of multiple slices, or two-dimensional images, that can be combined to generate a three dimensional image. CT imaging is particularly useful because it can show several types of tissue including lung, bone, soft tissue and blood vessels, with great clarity. Accordingly, such imaging of the body can be used to diagnose problems such as cancers, cardiovascular disease, infectious disease, trauma and musculoskeletal disorders.
CT imaging is commonly used to diagnose rib metastasis. Metastasis is the spread of cancer from its primary site to other places in the body. Rib metastasis is caused by cancerous cells from a primary tumor relocating to the ribs. Approximately 170,000 new cases of bone metastases are diagnosed annually in the United States. Over 500,000 Americans live with bone metastases. Primary carcinomas that frequently metastasize to bone include those from breast, lung, prostate, kidney, thyroid, stomach, and intestinal cancer.
In order to diagnose rib metastasis, a doctor typically searched for rib metastases in chest CT images generated from a CT volume data. A typical CT volume data set can contain hundreds of slices. FIG. 1 illustrates an exemplary axial slice 100 of a chest CT volume data set. The axial slice 100 is a view generated along an axial plane, which is orthogonal to the long axis of the body. As illustrated in FIG. 1, multiple ellipsoid shaped bright areas 102, 104, 106, 108, 110, and 112 can be seen in the axial slice 100. These ellipsoid shaped bright areas, 102, 104, 106, 108, 110, and 112 are the intersections of ribs with the axial plane. In order to diagnose rib metastasis, a doctor must typically look at hundreds of such slices and on each slice study each of the rib intersections to look for possible metastasis. This diagnosis process is very tedious and error prone.
Once a possible metastasis is discovered on a rib, the doctor needs to identify which rib it is. However, there are no specific features which differentiate ribs from one another. Furthermore, ribs typically cross through the axial planes at an oblique angle making their identification problematic. Accordingly, accurately identify a particular rib is typically a long and difficult process.